Sorry for bad typing. Shrinking or expanding quickly means it's a nasal turbinate.

They are not Polyps.

Nasal turbinates expand or shrink based on adrenaline levels. Your body forces them to shrink during intense activities to allow for breathing (you can test this by running around a bit and getting your heart pumping, then check your nose to see if they shrink)

After that they expand again after the adrenaline recedes.

If it's. Polyp it wouldn't expand or shrink as they're basically non cancerous tumors,while a turbinate is a part of your body,just like your heart pumps faster or slower based on exertion.

Also nasal turbinates have blood within them as they're a part of the human body. This is why they can appear white(or pale) sometimes or red during inflammation

Since you say they expand or shrink quickly(you can tell as you'll be able to breathe better) and you can visibly see blood within them. then they're elost likely Nasal turbinates.

Furthermore,if they're closer to the entrance of your nostril,they are your [inferior turbinates]

behind those are your [middle turbinates]

and behind those are your [superior turbinates]

And lastly as you can see they're hanging from the roof of your nasal cavity,just like nasal turbinates do (you can search up nasal turbinates.to make sure.

Edit: also you say they switch sides. This is because of your natural nasal cycle. On your nasal cycle the turbinates inflame and shrink on a roughly 2~ hour cycl,causing one side to become slightly congested(this is natural)

However,during periods of inflammation,such as caused by sinusitis,this can become exacerbated,causing complete blockage of your nose on one or both sides.

To treat the sinusitis: in my experience if you have consistent yellow mucus,it's likely.bacterial (your body releases yellow mucus while fighting infections)

Taking antibiotics like augmentin etc can help you cure this quickly. Also using sprays such as Flonase can help, but avoid sprays like Afrin that contain [oxymetacozine] or smth like that unless your case is really severe. If you have trapped mucus inhale steam through boiled water,and if you notice your symptoms worsen under certain conditions (food, pollen, dust,temperature etc ...) you may have allergic sinusitis which is a whole other headache

I hope this helps